In recent years, it has been considered to use resin particles having many recesses on the surface thereof in fields of a light diffusing agent, a light diffusing film, a light diffusing sheet, a light diffusing plate, and cosmetics which use the same because of a unique form of the resin particles.
Conventionally, a resin particle having many recesses on the surface, for example, obtained by a method comprising performing a seed dispersion polymerization of an aromatic vinyl monomer in a solvent wherein spherical particles of a methacrylate ester polymer are dispersed as seed particles, and drying the polymer, has been known as resin particles having many recesses on the surface thereof (see Patent Document No. 1).
However, resin particles having many recesses have problems, for example, upon using them as a light diffusing agent in a light diffusing film, a light diffusing sheet, a light diffusing plate and the like, in a case where they are applied on a film-like or sheet-like resin, resin particles dissolve to disappear in a solvent which is binder; in a case where a plate is formed by mixing and dispersing them into matrix resin, resin particles melt to disappear; and the like.
Accordingly, a resin particle having many recesses on the surface thereof, which possesses solvent resistance and heat resistance, has been expected.